This invention relates generally to water pollution control and the treatment of sewage as a part of a control program. More specifically, this invention pertains to control and removal of debris in sewage, such as rags, string, plastic sheeting scraps, etc., which are not biologically reducible in the treating process and tend to cause problems with respect to sewage flow and use of the sewage sludge product after treatment is completed.
There are various municipal approaches to treatment of sewage waste. One such approach involves aerobic digestion of sewage to produce a sludge which may be distributed in liquid form on arable land as fertilizer or may be dried in beds designed for such purpose to form a solid product of the treatment process.
A recurring problem in a typical aerobic digestion treatment facility is the presence of foreign matter which will not undergo reduction to solution during treatment and which will tend to clog lines, pumps, scum troughs or other apparatus of the facility. Such debris is also unslightly and undesirable if contained in the liquid sludge or dried solids which may be applied to lawns around homes, schools, churches or ballfields. In this latter instance, the presence of such debris clearly suggests the origin of the fertilizing material and is therefore generally socially unacceptable.
While comparatively large sewage treatment facilities can justify expensive automated equipment for removing debris from liquid sewage, municipalities having relatively small or intermediate systems or budget constraints which do not permit unusual capital expenditures nevertheless must contend with the debris problem.
The present invention comprehends, in one aspect, the provision of a unique but relatively simplified low cost means of sewage debris capture and removal which obviates the need for expensive equipment to perform this function. In another aspect, this invention comprehends a comparatively more sophisticated approach to debris removal from liquid sewage including means for automatically transporting collected debris from the treatment tank on a continuous basis.